1. Field of the Invention
The present invention relates to a driving circuit of a light emitting diode (LED). More particularly, the present invention relates to a driving circuit with a low cost.
2. Description of Related Art
An energy-saving concept is highlighted due to a global warming issue, so that designs of computer related equipments are also in accordance with the energy-saving concept. Since application of a light-emitting diode (LED) backlight module can reduce power consumption, and reduce a product size and generation of heat, the electronic product can be light and slim. Therefore, LEDs are widely applied to the backlight modules of displays.
A driving circuit of the LED backlight module generally includes a boost circuit and a dimming circuit, wherein the boost circuit is mainly used to convert an input voltage and provide a driving voltage for the LED backlight module, and the dimming circuit is used for adjusting a conducted current of the LED. The LED backlight module includes a plurality of LED strings, and each of the LED strings is composed of a plurality of LEDs connected in serial. A luminance of the LED is proportional to the conducted current, and the dimming circuit is used for adjusting a light-emitting intensity of the LED string.
The dimming circuit receives a pulse width modulation (PWM) signal and an enable signal, and adjusts the conductive current of the LED string according to the PWM signal and the enable signal. However, in a high-class electronic product, to even the light-emitting intensity of each LED string, multiple adjusting circuits have to be applied, and a large number of transmission gates are used for signal transmission. Therefore, not only a complexity of a circuit design is increased, a chip area is also increased, so that a cost of the device is increased.